Development of an input device such as a touch sensor has been in progress in recent years. For example, a capacitance type touch sensor is used in a touch panel etc., thereby enabling detection of input location information. An in-cell type touch panel, in whose display element a touch sensor is incorporated, and the like are also known.
By a research on prior art documents, the following documents have been found.
Proposed has been an array-type tactile feedback touch panel which includes: a touch control means; a vibrator such as an electret; a unit that causes such a vibrator on a track of movement to vibrate; and a display unit that displays a touch control screen (see Japanese Patent Application Laid-open No. 2011-8749).
Also, proposed has been a switching element which includes a p-channel transistor, and an electret film provided relatively movably thereto and capable of accumulating electric charges, and which uses electrostatic induction to control an ON-state and OFF-state of the p-channel transistor (see Japanese Patent Application Laid-open No. 2008-109772).
Further, proposed has been an input device, which includes: an operation panel having a plurality of conductive patterns crossing at right angles to each other; a (pen-like) pointer; and a position detecting means for measuring a potential due to electric charges generated in a plurality of conductive patterns by a charged part of the pointer in approach of the operation panel by the pointer and for detecting the position of the pointer based on the result of measurement of the potential, and in which an electret is used as the charged part of the pointer (see Japanese Patent Application Laid-open No. 2014-132422).
Moreover, proposed as a vibration detecting sensor device has been a device, whose sensor unit has: a vibration power-generating device for generating power through external vibration (an electret is used as one example); a power storage device for storing electric charges generated by the vibration power-generating device; and a determining unit for determining an amount of electric charges stored in the power storage device (see Japanese Patent Application Laid-open No. 2013-217701).
Additionally, proposed has been a no-contact type mechanism component in which: a gate electrode of a thin-film transistor is configured by an electret formed by polarizing a dielectric; the gate electrode is made movable freely to a gate insulating film; the channel conductance of the thin-film transistor is made changed by the movability; and an electric current between a source and drain is made variable (see Japanese Patent No. 58-49036).